Holding seal material and method for producing holding seal material

Abstract

Provided is a holding seal material including: alumina fibers, wherein the alumina fibers contain 85 to 98 wt % of an alumina component and 15 to 2 wt % of a silica component, the holding seal material has multiple marks formed by needle punching, and in a heat treatment test, a contact pressure of the holding seal material heated at a test temperature of 950° C. is 65 to 99% of a contact pressure of the holding seal material heated at test temperature of 800° C., wherein the heat treatment test includes: a compressing step of disposing the holding seal material between an upper plate and a lower plate and compressing the holding seal material to a gap bulk density (GBD) of 0.3 g/cm3; a heating step of heating, after the compressing step, the compressed holding seal material to a predetermined test temperature at a temperature-increasing rate of 45° C./min and maintaining the holding. seal material at the test temperature for six hours; a releasing step of cooling, after the heating step, the holding seal material to room temperature and releasing the holding seal material to a gap bulk density (GBD) of 0.27 g/cm3; and a cycling step of repeating, after the releasing step, 1000 times the cycle of re-compression of the holding seal material to a gap bulk density (GBD) of 0.3 g/cm3 and re-release of the holding seal material to a gap bulk density (GBD) of 0.27 g/cm3 so as to calculate the contact pressure (kPa) of the holding seal material by dividing the load at the last re-release in the cycling step by the area of the holding seal material.

1 . A holding seal material comprising:
 alumina fibers,   wherein the alumina fibers contain 85 to 98 wt % of an alumina component and 15 to 2 wt % of a silica component,   the holding seal material has multiple marks formed by needle punching, and   in a heat treatment test, a contact pressure of the holding seal material heated at a test temperature of 950° C. is 65 to 99% of a contact pressure of the holding seal material heated at a test temperature of 800° C.,   wherein the heat treatment test includes:   a compressing step of disposing the holding seal material between an upper plate and a lower plate and compressing the holding seal material to a gap bulk density (GBD) of 0.3 g/cm 3 ;   a heating step of heating, after the compressing step, the compressed holding seal material to a predetermined test temperature at a temperature-increasing rate of 45° C./min and maintaining the holding seal material at the test temperature for six hours;   a releasing step of cooling, after the heating step, the holding seal material to room temperature and releasing the holding seal material to a gap bulk density (GBD) of 0.27 g/cm 3 ; and   a cycling step of repeating, after the releasing step, 1000 times the cycle of re-compression of the holding seal material to a gap bulk density (GBD) of 0.3 g/cm 3  and re-release of the holding seal material to a gap bulk density (GBD) of 0.27 g/cm 3  so as to calculate the contact pressure (kPa) of the holding seal material by dividing the load at the last re-release in the cycling step by the area of the holding seal material.   
     
     
         2 . The holding seal material according to  claim 1 ,
 wherein in the heat treatment test, the contact pressure of the holding seal material heated at a test temperature of 950° C. is 80 to 99% of the contact pressure of the holding seal material heated at a test temperature of 800° C.   
     
     
         3 . The holding seal material according to  claim 1 ,
 wherein in the heat treatment test, the contact pressure of the holding seal material heated at a test temperature of 950° C. is 10 to 50 kPa.   
     
     
         4 . The holding seal material according to  claim 1 ,
 wherein the alumina fibers have an average fiber diameter of 5 to 8 μm.   
     
     
         5 . The holding seal material according to  claim 1 ,
 wherein inorganic particles are attached to the surface of the alumina fibers.   
     
     
         6 . The holding seal material according to  claim 5 ,
 wherein the inorganic particles are at least one selected from the group consisting of titania particles, silica particles, alumina particles, and magnesia particles.   
     
     
         7 . The holding seal material according to  claim 1 ,
 wherein the alumina fibers contain α-alumina in a proportion of 0.3 to 15 wt % relative to the weight of the alumina fibers.   
     
     
         8 . The holding seal material according to  claim 1 , further comprising at least one organic binder selected from the group consisting of a water-soluble or water-dispersed organic polymer, a thermoplastic resin, and a thermosetting resin. 
     
     
         9 . The holding seal material according to  claim 8 ,
 wherein the water-soluble or water-dispersed organic polymer is at least one selected from the group consisting of acrylic resin, acrylate latex, rubber latex, carboxymethylcellulose, and polyvinyl alcohol.   
     
     
         10 . The holding seal material according to  claim 8 ,
 wherein the thermoplastic resin is styrene resin.   
     
     
         11 . The holding seal material according to  claim 8 ,
 wherein the thermosetting resin is epoxy resin.   
     
     
         12 . The holding seal material according to  claim 8 ,
 wherein the holding seal material has an organic binder content of 0.1 to 9.0 wt % relative to the weight of the holding seal material.   
     
     
         13 . The holding seal material according to  claim 1 ,
 wherein at least one of the marks formed by needle punching is curved and penetrates the holding seal material.   
     
     
         14 . A method for producing a holding seal material including alumina fibers,
 the method comprising:   a spinning mixture preparing step of mixing an aqueous solution of basic aluminum chloride and silica sol to achieve a proportion of basic aluminum chloride of 82.8 to 97.7 wt % and a proportion of silica of 17.2 to 2.3 wt % to prepare a spinning mixture;   an alumina fiber precursor producing step of spinning the spinning mixture into alumina fiber precursors by a blowing method at 80° C. to 140° C.;   an aggregate producing step of collecting the alumina fiber precursors to produce an alumina fiber precursor aggregate having a moisture content of 5 to 10%;   a conveying step of moisturizing the alumina fiber precursor aggregate to a moisture content of 10 to 18% and conveying the alumina fiber precursor aggregate;   a sheet producing step of compressing the alumina fiber precursor aggregate into a sheet having a moisture content of 10 to 18%;   a needle punching step of needle punching the sheet under the condition of 2 to 50 marks/cm 2 ; and   a firing step of firing the sheet having a moisture content of 10 to 18% at 1200° C. to 1300° C.